This invention relates generally to valve devices, and more particularly to a high shear ball check valve device and a liquid ink image producing machine having same.
Prior art valve devices, including ball type check valves devices which will xe2x80x9ccheckxe2x80x9d the reverse flow of fluid through a flow line are well known. One typical problem with these prior art valve devices is that they are usually designed for high pressure applications with gravity or a spring return device on the flapper or a ball sealing member. As such, they are not very functional for ultra-low pressure actuation applications because they do not respond quickly and precisely to changes in low pressure flow condition, and do not provide for good sealing under such conditions. The inability of prior art valve devices to respond quickly and precisely to flow control or to changes in flow conditions, makes their use unacceptable for controlling liquid ink flow liquid ink image producing machine, for example a phase change ink image producing machine.
In general, phase change ink image producing machines or printers employ phase change inks that are in the solid phase at ambient temperature, but exist in the molten or melted liquid phase (and can be ejected as drops or jets) at the elevated operating temperature of the machine or printer. At such an elevated operating temperature, droplets or jets of the molten or liquid phase change ink are ejected from a printhead device of the printer onto a printing media. Such ejection can be directly onto a final image receiving substrate, or indirectly onto an imaging member before transfer from it to the final image receiving media. In any case, when the ink droplets contact the surface of the printing media, they quickly solidify to create an image in the form of a predetermined pattern of solidified ink drops. Such molten ink ordinarily needs to be transported and controlled precisely, by devices including a check valve for example, between a melting station and such printhead device.
An example of such a phase change ink image producing machine or printer, and the process for producing images therewith onto image receiving sheets is disclosed in U.S. Pat. No. 5,372,852 issued Dec. 13, 1992 to Titterington et al. As disclosed therein, the phase change ink printing process includes raising the temperature of a solid form of the phase change ink so as to melt it and form a molten liquid phase change ink. It also includes applying droplets of the phase change ink in a liquid form onto an imaging surface in a pattern using a device such as an ink jet printhead. The process then includes solidifying the phase change ink droplets on the imaging surface, transferring them the image receiving substrate, and fixing the phase change ink to the substrate.
Conventionally, the solid form of the phase change is a xe2x80x9cstickxe2x80x9d, xe2x80x9cblockxe2x80x9d, xe2x80x9cbarxe2x80x9d or xe2x80x9cpelletxe2x80x9d as disclosed for example in U.S. Pat No. 4,636,803 (rectangular block, cylindrical block); U.S. Pat. No. 4,739,339 (cylindrical block); U.S. Pat. No. 5,038,157 (hexagonal bar); U.S. Pat. No. 6,053,608 (tapered lock with a stepped configuration). Further examples of such solid forms are also disclosed in design patents such as U.S. Pat. No. D453,787 issued Feb. 19, 2002. In use, each such block form xe2x80x9cstickxe2x80x9d, xe2x80x9cblockxe2x80x9d, xe2x80x9cbarxe2x80x9d or xe2x80x9cpelletxe2x80x9d is fed into a heated melting device that melts or phase changes the xe2x80x9cstickxe2x80x9d, xe2x80x9cblockxe2x80x9d, xe2x80x9cbarxe2x80x9d or xe2x80x9cpelletxe2x80x9d directly into a print head reservoir for printing as described above.
Conventionally, phase change ink image producing machines or printers, particularly color image producing such machines or printers, are considered to be low throughput, typically producing at a rate of less than 30 prints per minute (PPM). The throughput rate (PPM) of each phase change ink image producing machine or printer employing solid phase change inks in such xe2x80x9cstickxe2x80x9d, xe2x80x9cblockxe2x80x9d, xe2x80x9cbarxe2x80x9d or xe2x80x9cpelletxe2x80x9d forms is directly dependent on how quickly such a xe2x80x9cstickxe2x80x9d, xe2x80x9cblockxe2x80x9d, xe2x80x9cbarxe2x80x9d or xe2x80x9cpelletxe2x80x9d form can be melted down into a liquid. The quality of the images produced depends on such a melting rate, and on the subsystems and devices such as flow control check valves, employed to control the phase change ink liquid.
There is therefore a need for an efficient and fast responsive check valve device, and one that is suitable for use in the controlling of liquid ink flow in a liquid ink image producing machines.
In accordance with the present invention, there is provided a high shear ball check valve device that is suitable for use in a liquid ink image producing machine to quickly and precisely control flow of liquid ink. The high shear ball check valve device includes a valve housing defining a valve chamber. The valve chamber has a desired cross-dimension, an inlet end, and an outlet end. The high shear ball check valve device also includes an inlet member that is connected to the valve housing and has an inlet opening and a ball seat and seal portion surrounding the inlet opening. The ball seat and seal portion has a desired first durometer hardness value. The high shear ball check valve device next includes a valve ball having a desired diameter and being located movably within the valve chamber, and an outlet opening located at the outlet end of the valve chamber. The outlet opening has a rectangular shape, and a size that is slightly greater than the diameter of the valve ball, for creating a backward fluid flow pattern that results in relatively high shear stress on the valve ball. The relatively high shear stress thereby quickly moving the valve ball away from the outlet opening and back against the ball seat and seal portion to shut off the inlet opening.